title: Transient elastohydrodynamic lubrication analysis of a novel metal-on-metal hip prosthesis with a non-spherical femoral bearing surface.
abstract: Effective lubrication performance of metal-on-metal hip implants only requires optimum conformity within the main loaded area, while it is advantageous to increase the clearance in the equatorial region. Such a varying clearance can be achieved by using non-spherical bearing surfaces for either acetabular or femoral components. An elastohydrodynamic lubrication model of a novel metal-on-metal hip prosthesis using a non-spherical femoral bearing surface against a spherical cup was solved under loading and motion conditions specified by ISO standard. A full numerical methodology of considering the geometric variation in the rotating non-spherical head in elastohydrodynamic lubrication solution was presented, which is applicable to all non-spherical head designs. The lubrication performance of a hip prosthesis using a specific non-spherical femoral head, Alpharabola, was analysed and compared with those of spherical bearing surfaces and a non-spherical Alpharabola cup investigated in previous studies. The sensitivity of the lubrication performance to the anteversion angle of the Alpharabola head was also investigated. Results showed that the non-spherical head introduced a large squeeze-film action and also led to a large variation in clearance within the loaded area. With the same equatorial clearance, the lubrication performance of the metal-on-metal hip prosthesis using an Alpharabola head was better than that of the conventional spherical bearings but worse than that of the metal-on-metal hip prosthesis using an Alpharabola cup. The reduction in the lubrication performance caused by the initial anteversion angle of the non-spherical head was small, compared with the improvement resulted from the non-spherical geometry.
authors.affiliation: Institute of Medical and Biological Engineering, School of Mechanical Engineering, University of Leeds, Leeds, UK. mnqm@leeds.ac.uk
authors.forename: Q E
authors.initials: QE
authors.lastname: Meng
authors.forename: F
authors.initials: F
authors.lastname: Liu
authors.forename: J
authors.initials: J
authors.lastname: Fisher
authors.forename: Z M
authors.initials: ZM
authors.lastname: Jin
mesh_terms: D001698:Biomedical Engineering; D002858:Chromium Alloys; D004548:Elasticity; D019544:Equipment Failure Analysis; D006622:Hip Prosthesis; D006801:Humans; D057446:Hydrodynamics; D066298:In Vitro Techniques; D008153:Lubrication; D053768:Metal Nanoparticles / Q000009:adverse effects; D011474:Prosthesis Design; D013499:Surface Properties
chemical_list: D002858:Chromium Alloys